Comparative measurement of spinal CSF microdialysate concentrations and concomitant antinociception of morphine and morphine-6beta-glucuronide in rats.
Life Sci
; 80(14): 1319-26, 2007 Mar 13.
Article
em En
| MEDLINE
| ID: mdl-17258777
ABSTRACT
Morphine-6beta-glucuronide (M6G) is well known as a potent active metabolite in humans. To clarify concentration-antinociceptive effect relationships for morphine and M6G, we evaluated comparatively the pharmacokinetics and antinociceptive effects of morphine and M6G. The spinal CSF concentration and antinociception were simultaneously measured by using the combination of a microdialysis method and the formalin test in conscious rats after the s.c. administration of morphine (0.3-3 mg/kg) and M6G (0.1-3 mg/kg). The plasma concentration of M6G after s.c. administration was higher than that of morphine, as shown by the 2.1 times greater value of area under the concentration-time curve (AUC(plasma)). The spinal CSF concentrations of morphine and M6G increased dose-dependently. The AUC(CSF) of M6G was 1.6-1.8 times higher than that of morphine at each dose. Administration of morphine and M6G dose-dependently suppressed the flinching behavior induced by formalin injection. The ED(50) values for M6G were 3 times lower than those of morphine, although the spinal CSF concentration versus antinociceptive effect curves of morphine and M6G were very similar, with similar EC(50) values. These results suggest that the antinociceptive potencies of morphine and M6G, evaluated by simultaneous measurements of spinal CSF drug concentration and antinociception, are equivalent. Simultaneous measurement of spinal CSF concentration and antinociception by using microdialysis should be useful for elucidating the relationship between pharmacokinetics and pharmacodynamics of various opioids.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Dor
/
Medula Espinal
/
Líquido Cefalorraquidiano
/
Analgésicos Opioides
/
Morfina
/
Derivados da Morfina
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
Life Sci
Ano de publicação:
2007
Tipo de documento:
Article